linux-kernel - Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk and pte prefetch

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Date:	Mon, 05 Jul 2010 17:09:19 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk
 and pte prefetch



Avi Kivity wrote:

> 
> I'm not convinced we can bypass the checks.  Consider:
> 
> 
> VCPU0                 VCPU1
> 
> #PF
> walk_addr
> -> gpml4e0,gpdpe0,gpde0,gpte0
> 
>                       replace gpdpe0 with gpdpe1
>                       #PF
>                       walk_addr
> -> gpml4e0,gpdpe1,gpde1,gpte1
>                       fetch
>                       -> establish hpml4e0,hpdpte1,hpde0,hpte1
> fetch
> read hpdpe1
> if (present(hpdpe1))
>     continue;
> ...
> write hpte0 using shadow hieratchy for hpte1
> 

Ah, i missed this case, thanks for you point it out, i'll fix it in
the next version.
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